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pythonraspberry-piprivileges

DietPi - running a script manually works - but starting from postboot.d throws I/O error

I'm trying to run a script automatic when booting Raspberry with DietPi. My script starts a Python3 programm which then at the end starts an external program MP4Box which merges 2 video files to a mp4 in a folder in my lighttp webserver.

When I start the script manually everything works. But when the script starts automatically on boot, when it comes to the external program MP4Box, I get an error:

Cannot open destination file /var/www/Videos/20201222_151210.mp4: I/O Error

Script starting my pythons is "startcam" - which lies in the folder /var/lib/dietpi/postboot.d

#!/bin/sh -e
# Autostart RaspiCam
cd /home/dietpi
rm -f trigger/*
python3 -u record_v0.1.py > record.log 2>&1 &
python3 -u motioninterrupt.py > motion.log 2>&1 &

the readme.txt in postboot.d says:

# /var/lib/dietpi/postboot.d is implemented by DietPi and allows to run scripts at the end of the boot process:
# - /etc/systemd/system/dietpi-postboot.service => /boot/dietpi/postboot => /var/lib/dietpi/postboot.d/*
# There are nearly no restrictions about file names and permissions:
# - All files (besides this "readme.txt" and dot files ".filename") are executed as root user.
# - Execute permissions are automatically added.
# NB: This delays the login prompt by the time the script takes, hence it must not be used for long-term processes, but only for oneshot tasks.

So it should also start my script with root priviledges. And that is the (part of the) Script "record_v0.1.py" that throws the error:

import os
os.system('MP4Box -fps 15 -cat /home/dietpi/b-file001.h264 -cat /home/dietpi/a-file001.h264 -new /var/www/Videos/file001.mp4 -tmp ~ -quiet')

When I start the python programs manually (logged in as root) with:

/var/lib/dietpi/postboot.d/startcam

everythin is OK and instead of the error I get the message:

Appending file /home/dietpi/Videos/b-20201222_153124.h264
No suitable destination track found - creating new one (type vide)
Appending file /home/dietpi/Videos/a-20201222_153124.h264
Saving /var/www/Videos/20201222_153124.mp4: 0.500 secs Interleaving

Thanks for every hint

Solution

  • Contrary to the description, the scripts in postboot.d are not excuted as root. So I changed my script to:

    #!/bin/sh -e
# Autostart RaspiCam
cd /home/dietpi
rm -f trigger/*
sudo python3 -u record_v0.1.py > record.log 2>&1 &
sudo python3 -u motioninterrupt.py > motion.log 2>&1 &

    Now they are running as root and everything works as wanted.